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Yamaha 6YC water pressure gauge not working


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Hi all, I’ve had my Yamaha 6YC gauges since my 2200 TRS with F150xb was new in November 2015.  The factory installed the water pressure sensor for the gauge because I have a jack plate and it has worked fine until this trip. I had the boat serviced in November but didn’t use it until today. The water pressure reading lights up but never moves from the lowest point. I do have positive pressure though and the temp gauge works fine.  Ran it for about 2 hours today and no issues at all so I am sure it has appropriate water pressure. I disconnected and reconnected the wire harness and that didn’t fix it...shocking 😎 Nothing looks out of the ordinary and it only has 130 hours. Under warranty until November 2021. Anyone have any thoughts on what to check?  Could the sensor be bad and if so would the gauge still light up or would it not show anything at all?  I checked the 6YC manual and it was less than helpful. I plan to call the service place on Monday but doubt they will get to it this week and then I am not back for another month. Any thoughts would be appreciated. Thank you!

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Thanks for the reply. I checked and saw nothing that looked out of place and nothing looked missing. No rubber tube.  It has a wire harness marked with two Ws. I checked the hose inlet fitting that you can use attached a hose to flush the motor, although I always use the earmuffs. Not sure what they used, assuming they started it (it was on the trailer and I know they don’t dip it). I will connect a hose to it tomorrow and start it...maybe something got stuck in there or in the sensor plug itself? 

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I am repairing a very similar problem, although on a different Yamaha model. I have a Yam F250 and the square gauge setup, but recently got the Simrad engine panel working on my EVO 3. I only show one bar of water pressure, maybe two at high rpms. After trying all the easy stuff, I took the boat to my service guy for a yearly service, and asked him to see if he could fix it. No temp problems.

There’s a small fitting on the engine block that senses pressure and routes to panel. He sent the following pics this morning. The blockage is mostly sand, and some salt I suppose. I’m also not sure what piece goes where, but the bottom pic shows the exit port from the block.

He has cleaned and reinstalled in the block. Water test in a few days, but he Is certain that this is the problem.

Of course, now I have a new concern, what do the rest of the cooling system passages look like. 

PM me if you need additional info.....I can ask my guy for a better explanation.

Hope this helps!


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Thanks Frozen and Smilemaker, I will check as soon as I get it out of the water later this week. I think this will be it..great pics. Yesterday it hit the second bar at wot then actually worked fine for about 5 minutes then went back to one bar only. Odd design. I run pretty shallow a lot but usually grass and not sand so maybe on,y an every 4 year thing for me...Ben 

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